Fuse for an explosive projectile



Y 1957 .1. H SCHULER ET AL 2,791,963

FUSE FOR AN EXPLOSIVE PROJECTILE Filed Oct. 20. 1954 FIG. 2 G5 A INVENTORS JOHANNES HERMANN SCHULER ULRB C Ij THEILE ATTORNEY United States Fatent G FUSE FOR AN EXPLOSIVE PROJECTILE Johannes Hermann Schuler, Uterluss, Kreis Celle, and

Ulrich Theile, Steinhorst Uber Celle, Germany, assignors to Aktiebolaget Bofors, Bofors, Sweden, a Swedish corporation Application October 20, 1954, Serial No. 463,577

11 Claims. (Cl. 10270.2)

The present invention relates to fuses for explosive projectiles and other missiles, and more particularly to self-arming and self-igniting fuses.

One of the objects of the present invention is to provide a novel and improved fuse of the general class above referred to, the operating mechanism of which is entirely inert when and as long as a projectile equipped with the fuse is at rest (as distinguished from a projectile in flight) and is automatically activated when the projectile is in flight.

Another object of the invention is to provide a novel and improved fuse having an operating mechanism actuated by a potential source of energy which produces the energy required for activating the fuse mechanism only in response to -a physical magnitude acting upon a projectile in flight but is entirely inert until the projectile is fired thereby effectively preventing a detonation of the projectile by accidental impact against its fuse or similar causes.

Still another object of the invention is to provide a novel and improved fuse with an operating mechanism including a circuit system which by the action of said physical magnitude for a predetermined period of time is energized sufliciently to initiate the ignition of the fuse in response to an impact caused for instance by the projectile hitting a target and which after a further predetermined period of time is energized sufficient to initiate the ignition of the fusewithout the agency of an i the advantage that iid ioi tq T nfuse b' j mea e m ed. q r djbyf h is aimed? A turt e?! ld t-9f the s i mpro edit a; .t s automaticallyfreverts J f, defect the mechanism fails: the fuse passed, or mother words if .projectilefis atdud... T

affords theadvantage that the fuse of such a ducl aif ter.it

Other and; further fob ears," features and. ,advan ges of the invention 'willbe fpointejd page s plication.

fi i i' h fi it on. he both; hep iod f'tinie for fdetonatipn y impact and theperiod of time for= self detonatio h e In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1 is a sectional longitudinal view of a projectile equipped with a fuse according to the invention, and

Fig. 2 is a circuit diagram of the operating mechanism of the fuse.

Referring now to the figures in detail, the projectile according to Fig. 1 comprises a shell 'case 1, to the forward end of which the fuse according to the invention is screwed, separated from the shell casing by a flanged screw washer 4. The operating mechanism of the fuse is disposed within a metal fuse casing composed of a rear part 2 and a nose part 3. In this connection it may bementioned that a fuse according to the invention may also be mounted in or on a part of the projectile other than the nose end thereof, such as the rear part of the shell.

The shell case 1 is filled with bursting or explosive charges 5 and 6. The relation and coaction of these two charges are not essential for the understanding of the invention.

The operating mechanism of the fuse which is disposed in casing 2, 3, comprises two preferably cylindrical capacitors 7 and 8, separated by a partition wall formed within-the fuse casing by casing part 2, a resistor 9 preferably fitted in an annular groove of said partition wall and a circuit control means in form of a discharge tube 10 fitted in the space circumscribed by capacitor 7. The outer wall of capacitor 7 together With the respective wall portions of easing part 2 form an annular chamber 11 from which extend one or several rearwardly slanted ducts or channels 12 leading to the outside wall of fuse part 2. Each of these channels is lined with a metal tube 13, electrically insulated from casing part 2. The outer end of each channel 12 is plugged by means of a plug 14- made of lead or other comparative soft material. The closed spaces formed by channels 12 and chamber 11 are filled with a non-conductive powderized material such as glass orcolophony. The fuse mechanism further comprises an electrical detonating or igniting device 16 and a detonation initiator 17, both of conventional design and=,,disp0sed below capacitor 7 and encased by a generally cup=shaped member 20." The 'mechanism finally corru prises a switch '18" disposed in an aXiat-b'ore'of nose part 3 of the fusecasing Tlaisswitch is normally operrand can' -b clos'ed'by'an-imp'act experienced thepro'jectilejf or morei'specific'ally' by the fuse'thereof. The switch is" 1 diagrammaticallys'hown as comprisinganupper contactlf 19and' a lower contact 19,*the latter being' insulated' from nose part 3 bya'n insulation disc 21'.

The circuit connections of the aforedescribed me;- ponents of the'fuse mechanism areshown in Fig. 2. AccQrding to thisfigure, one of the electrodes of capacitor "'7 is connected tome'tal tubes 13 and the other is grounded, that'is, it isconnected"to -thefuse casing or to thepart 2 I thereof onlyfin which eveiit casingifpar't 3may bem adeQi ofhon-conductivemateriah Capacitor s andresistor 9 are'coiinected in seriesacrossthelterminals" ofcapacitor 7, and discharge tube 10 and -igniter' 15 are connected, in series a'ci'o's's the terminals of capacitor8. Finally; switch I 18-is connected-across the terminals of tube 10." Allthe components of the circuit system are, of course, 'lsuitahl y insulatedone froin member but the insulation'materials used for this purpose have preferably a finite value for a prposewhich be more fully: explainedv herein- A; isap'pare'iit, there 'is no energy"available which eration' of the fuse hereinbefoi'ef described, ,1

could cause-activationof detonator 16 even though switch contacts 18- were closed for instance-by an accidentalimpact when and as long as the projectile is at rest, or in other words, the fuse according to the invention is completely safe: priorto firing of the projectile-'mounting the fuse:

Let it now be assumed that the projectile is fi'red', say. from a rifled barrel. The centrifugal forceacting upon theaspinning projectile in: fiight willcauseexpulsion. of plugs 14. As.a.result,-thepowderedmaterial15in-chame berll; and ducts=12 will beejected. After leaving: the ducts, the powdered particles will come in contact with the: res'pectivewallv portions: of easing part l connected-to one-electrode. of capacitor: 7 The' friction between the powderednpaiticlesi and. tubes 13 which -are connected 15 with;,the other electrodeof'sc'apac'itor 'l willtgene'ra-te anelectrostaticcharge' and .carry' thcgelectrons. of this charge from:,one. eleotrode of. capacitor: 7 to the .other electrode-"- ereof; Consequently, capacitor; 7 will be: gradually chargedaduring; the ejection ofathe powdered-particless 0 Asa-1 6 eharge oficapacitor 7 increases-,1 ihwill begin to chargeLcapacitQn-B. The ratezofi charge at which capacitor 8 is charged obviously depends upon the capacitanees ofv capacitors; 7- and .8; and.the: ohmic: resistance of resistor 9.-

The; chargeof; capacitor, 8- increases untilethis. charge" has reached a predetermined maximum value correspond-- ing to the potential requiredifortube 10 to become conductive; Asa soonqasgthe. tube becomes.conductive;t.ca-.. paciton 8 discharges throughydetonatorslfi. vAs a result p detonator lid-initiates throughthe initiat'or'l'l the-.detona tion of thezexplosive charges 5 and 6. ofthe. projectile.

The aforedescribed detonation ofthe projectile by the agency of tube 10 constitutes the. aforementioned. selfdestroyingfeatureof the fuse.

Let itnow be assumed that the projectile strikesa targetv prior to capacitor 8 reaching the break-down potential. of. tube 10. butafter having been charged to apredetermined' intermediate value. Then the impact ofthe target against. the-fuse willi close switch, contactsglS thereby. shortcirs 40 cuiting tube 10. The intermediate;charge ofv capacitor .8 is nowsufficient to cause, the, capacitor, to discharge: through detonator 16 whereby the detonation of the pro-' jectileisinitiatei.

Asappearsfrom the previous description, the fuseis'rl5 armed for operation byimpact only for ,therpen'odcf time. required by capacitor 8 toincrease its predetermined in; termedi'ate charge to.-its predetermined; maximum charge; at which. it. can. discharge: through tube. 10. The; initial; period oftime betweennthe firing of. the: projectile; and, untilfcapacitm 8. reaches its, predetermined intermediate chargef constitutes a safety factor. This safetyvfactort. can be conveniently controlled. by, suitably'correlating; the; capacitors and ..the resistor; it may be such thatlhetpror; jectile {must .tr'a'vel. a. distance between-.770 and. 200 -ft., or: more from the muzzlegof. the barrel beforetitsfuseuber comesarmed.

Finally, let-itbe assumed that for any reason-such as.

a defect, the. projectile isv not automatically destroyed when capaciton hasreached its maximum, finalcharge As. previously mentioned, the insulation materials used for insulating .the respective components ofthefuseare; oflfi'nite values. These values are so selected that the charges ofcapacitors 7'and 8 are substantially dissipated. during the, time tlieprojectile is in flight. Consequently, theifusesis reverted to its initial energy-less or inoperativev condition at aboutthe time it falls back on the ground This feature permits service personnel to collect.duds.-and-- to disassemble the same without danger and also protects. the civilian population.

As appears from the ,previous description, particularly from the discussion of Fig. 2', the circuit means including, capacitor 8 and resistor 9 function as an ignition circuit in'wliich capacitor 8" constitutes the ignition capacitor, The capacitor 7 together with the fuse casing and"'t ubes 13 connected thereto function as an energizing circuit in which capacitor 7 constitutes-the sourceof power: Accordingly, capacitor 7 is sometimes referred to as power capacitor. It is further evident that the concept of the invention is not limited to using a capacitor as source of power or as storage for energy although the use of a capacitor is the preferred form of the invention. An alternative power supply may be formed by an electrostatic generator which isdriven bya physical magnitude acting upon the projectile when in flight, such as the centrifugal force developed by the spinning of theprojectile. Another meansv of: generating the. necessary energy during the flight of the projectile is a dynamo: r0- tated by the forces resulting from the spinning. of the projectile;

While the invention has been describedi in detail with respect to a certain now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention, that various. changes and modifications: may be; made; without departing; from the. spirit and: scope of: -the1invention, :.:and-. it is intended, therefore, to coverall suchzchangeszand modifications in the appended. claims.

Whatis claimed as: new and desired to: be secured. by Letters Patent is:

1. A self-arming and. self-ignitingfuse fon an explosive missile; comprising fuse ignition. mean's;-.circuit means: co.- acting with said ignition means for igniting the same in response to an energization of said circuit means, energizingrneans connected with said circuit means for' supplying energy to the same,: said energizing means includingpower. capacitance means and a metal fuse casingincludingfia chamber, powdered insulation 1 material} in saidchamber, said casing having at leastone ductleading from. said chamber. to the outside of thecasing'at a'slant. rearwardly relative to-the directionofflight.ofthe' missile, a metallining. for. saidduct electrically insulated from said casing, one electrode of said power capacitance means-being connected to said-lining, and the-.otherrto saidcasingwliereby the. powdered materialis ejected from sai'd'chamber when said missile is in flight. andathefriction between said material and said liningand the contact of'ej'ected material with said casing effect charging of said'ipowercapacitance means, the energizing means-being gradually'charged froman initial'substantially zero minimumcharge to a maximum charge by said. ejection of. the powdered material, said. maximum. charge energizing. said" circuit means for igniting. the ignition means, and. normally open switch means connected. in. a circuit. in cluding said circuit means and saidenergizing means, .said switch'means ble'ingcl'osed by an impact experienced by thefuse', closing of saidswitch' means effecting energi za-v tion'of'saidcircuit means for theflpurposc aforesaid only Whenthech'arging' of saidenergizi'ng means is above a predetermined intermediate value.

211A fuse according to'cla'im '1, wherein the. said circuit means include:circuit'control'means activating saidcircuit means for'igniting said ignition means in response to said maximum-charge; saidswitch means being connect'edin shuntt'osa'idcontrol means for'short'circuiting the same by cl'osingof the switch means whereby the charge. required to" energize" said circuit' means is reduced to said intermediate value.

32- A fuse'accordingto claim 2, wherein the said circuit control means comprise dischargetubemeans, said tube means becoming-conductive in' responseto said maximum charger 4l- A fuse according to claim 1', wherein the saidcircuit' means 'incliide:ignition'capacitance means; circuit'control meansan'dsaid ignition'means; said control meansr'being.

responsive'to' said maximum charge to elfect'v discliatgef ofsaid ignition capacitance means forthepurpose aforesaidja'nd' wherein the-said energizing means are connected in a charging circuit .includiiigsaid power. capacitance. means withsaid'ignition capacitance means.

57 A fuse according to claim 4, wherein the said circuit means further include time-delay means delaying charging of said ignition capacitance means by said energizing means for a predetermined period of time.

6. A fuse according to claim 5, wherein the said time delay means comprise resistance means.

7. A fuse according to claim 6, wherein the said ignition capacitance means and said resistance means are connected in series across the terminals of said power capacitance means, and wherein the said ignition means and the said circuit control means are connected in series across the terminals of the ignition capacitance means, and wherein the said switch means are connected across the terminals of the circuit control means.

8. A fuse according to claim 7, wherein the resistances of the insulation materials insulating the components of said circuit means and said energizing means one from another have values such that upon a failure of the fuse to be ignited in response to a maximum charge of said energizing means, the charges of both the capacitance means are gradually dissipated whereby the fuse is rendered inoperative for ignition by impact.

9. A self-arming and self-igniting fuse for an explosive missile spinning when in flight, said fuse comprising electrically operable fuse ignition means, circuit means connected to said ignition means for operating the same upon energization of said circuit means, means for energizing said circuit means, said energizing means comprising a metal fuse casing including a chamber, powdered insulation material in said chamber, said casing having at least one duct leading from said chamber to the outside of the casing at a slant rearwardly relative to the direction of flight of the missile, a metal lining in said duct electrically insulated from said casing, and capacitance means having one electrode connected to said lining and the other to said casing whereby the powdered material is ejected from said chamber when the missile is in flight and the friction between the said material and said metal lining and the contact of the ejected material with the casing effect charging of said capacitance means, the charge of the capacitance means being fed to said circuit means to energize the same for igniting said ignition means in response to a capacitor charge above a pre-determined value.

10. A fuse according to claim 9 and further comprising impedance means included in said circuit means and normally open switch means closable by impact and connected in shunt with said impedance means, closing of said switch means short circuiting said impedance means to energize said circuit means for operating the ignition means in response to a capacitor charge of a pre-determined value below the aforesaid pre-determined value.

11. A fuse according to claim 9, wherein a plug is inserted in the outer end of said duct for sealing the same, the said plug being fitted for ejection by the effect of the centrifugal force acting upon the fuse when the missile is in flight.

References Cited in the file of this patent UNITED STATES PATENTS 1,858,969 Ruhlemann May 17, 1932 FOREIGN PATENTS 487,039 Germany Nov. 30, 1929 101,601 Sweden May 13, 1941 

